The present invention concerns methods of diagnosis and treatment of diseases or conditions characterized by abnormal cellular signal transduction. The invention is based on the observation that molecules believed to play an important role in cellular signal transduction contain a unique domain that can bind to signal transduction pathway components thereby influencing cellular events. The following is a discussion of relevant art, none of which is admitted to be prior art to the invention.
Receptor tyrosine kinases belong to a family of transmembrane proteins and have been implicated in cellular signaling pathways. The predominant biological activity of some receptor tyrosine kinases is the stimulation of cell growth and proliferation, while other receptor tyrosine kinases are involved in arresting growth and promoting differentiation. In some instances, a single tyrosine kinase can inhibit, or stimulate, cell proliferation depending on the cellular environment in which it is expressed. (Schlessinger, J. and Ullrich, A., Neuron, 9(3):383-391, 1992.)
Receptor tyrosine kinases are composed of at least three domains: an extracellular ligand binding domain, a transmembrane domain and a cytoplasmic catalytic domain that can phosphorylate tyrosine residues. Ligand binding to membrane-bound receptors induces the formation of receptor dimers and allosteric changes that activate the intracellular kinase domains and result in the self-phosphorylation (autophosphorylation and/or transphosphorylation) of the receptor on tyrosine residues. Individual phosphotyrosine residues of the cytoplasmic domains of receptors may serve as specific binding sites that interact with a host of cytoplasmic signalling molecules, thereby activating various signal transduction pathways (Ullrich, A. and Schlessinger, J., 1990, Cell 61:203-212).
The intracellular, cytoplasmic, non-receptor protein tyrosine kinases do not contain a hydrophobic transmembrane domain and share non-catalytic domains in addition to sharing their catalytic kinase domains. Such non-catalytic domains include the SH2 domains (SRC homology domain 2; Sadowski, I. et al., Mol. Cell. Biol. 6:4396-4408; Koch, C. A. et al., 1991, Science 252:668-674) and SH3 domains (SRC homology domain 3; Mayer, B. J. et al., 1988, Nature 332:269-272). Such non-catalytic domaims are also thought to include the PH domain (Musacchio et al., 1993, TIBS 18:342-348). The noncatalytic domains are thought to be important in the regulation of protein-protein interactions during signal transduction (Pawson, T. and Gish, G., 1992, Cell 71:359-362).
A central feature of signal transduction (for reviews, see Posada, J. and Cooper, J. A., 1992, Mol. Biol. Cell 3:583-392; Hardie, D.G., 1990, Symp. Soc. Exp. Biol. 44:241-255), is the reversible phosphorylation of certain proteins. Receptor phosphorylation stimulates a physical association of the activated receptor with target molecules. Some of the target molecules are in turn phosphorylated. Such phosphorylation transmits a signal to the cytoplasm. Other target molecules are not phosphorylated, but assist in signal transmission by acting as adapter molecules for secondary signal transducer proteins. For example, receptor phosphorylation and the subsequent allosteric changes in the receptor recruit the Grb-2/SOS complex to the catalytic domain of the receptor where its proximity to the membrane allows it to activate ras Pawson, T. and Schiessinger, J., Current Biol. 13:434, 1993.
The secondary signal transducer molecules generated by activated receptors result in a signal cascade that regulates cell functions such as cell division or differentiation. Reviews describing intracellular signal transduction include Aaronson, S. A., Science, 254:1146-1153, 1991; Schlessinger, J. Trends Biochem. Sci., 13:443-447, 1988; and Ullrich, A., and Schlessinger, J., Cell, 61:203-212, 1990.
Abnormalities in signal transduction pathways can lead to various diseases in at least three different ways: (1) underactivity (2) mutation, and (3) overexpression. An example of underactivity is observed in some forms of diabetes. Examples of mutation include the role of BCR-ABL in chronic myelogenous leukemia and acute lymphocytic leukemia. Pendergrast et al., 1993, Cell 75:175-185.
Overexpression of certain protein tyrosine kinases has been shown to subvert normal growth control pathways and lead to oncogenesis (reviewed in Hunter, T., 1991, Cell 64:249-270). An example of a protein that may participate in the aberrant growth of breast cancer cells is HER2, also known as c-erbB-2 (Coussens et al. , 1985 Science 230:1132-1139; Yamamoto et al., 1986, Nature, 319:521-527). This receptor was also isolated as the rat oncogene neu, an oncogene responsible for chemically induced rat glioblastomas (Padhy et al., 1982 Cell, 28:865-871; Schechter et al., 1984 Nature 312:513-516; Bargmann et al., 1986, Nature, 319:226-230). HER2/erbB-2 is known to be amplified and overexpressed in about 25% of human breast cancers (Slamon et al., 1987 Science 235:177-182; Slamon et al., 1989 Science 244:707-712).